K-252a is a physiologically active substance produced by microorganisms (Japanese Patent Laid-Open Application No. 41489/1985). It has an inhibition activity for protein kinase C and exhibits various pharmacological effects.
A conventional purification process of K-252a comprises the steps of: a) collecting microorganisms by filtering a culture solution; b) extracting the microorganisms by adding thereto a hydrous or anhydrous organic solvent such as methanol or acetone; c) removing the microorganisms by filtration; d) concentrating the resulting extracted solution; e) further extracting it with an anhydrous organic solvent in high yields; f) separating it by using a column filled with adsorbents such as active carbon or Diaion HP-10 and carriers such as silica gel, silanized silica gel, aluminum oxide or dextran; and g) concentrating it to obtain a crude K-252a crystal. However, the crystal thus obtained will not have sufficient purity. This process therefore further needs a recrystallization step in order to achieve higher purity. Furthermore, this process is not suitable for filtering a large amount of the culture solution because it is considerably difficult to filter the culture solution in this process.
Alternatively, it is also possible to collect an extracted solution by directly extracting a culture solution with an organic solvent and then filtering it. However, this process further needs a column treatment because the organic solvent used for extraction should be added in the same volume as the culture solution or more due to a lower solubility of K-252a in various solvents (5 to 10 g/l, for example 5 g/l in acetone), a liquid volume to be treated is extremely increased and the resulting extracted solution has lower purity.